The present invention generally relates a pattern matching apparatus of a communication apparatus with employment of a multi-value modulation method. More specifically, the present invention is directed to such a pattern matching apparatus that even when a length of a pattern is extended, a total number of adders as well as a total number of D-FFs (D type flip-flops) are not increased.
Referring now to drawings, the conventional pattern matching apparatus will be described. FIG. 9 is a schematic block diagram for representing an arrangement of one conventional pattern matching apparatus. FIG. 10 illustrates a frame format used to explain operation of the conventional pattern matching apparatus depicted in FIG. 9.
As represented in FIG. 10, in the conventional pattern matching apparatus, the known symbol pattern (normally, called as a "synchronization word" or a "unique word", and will be referred to as a "UW pattern (unique word pattern) hereinafter)" is detected from the received signal, and this known symbol pattern is utilized as follows:
To synchronize a frame/slot, PA1 To detect a head symbol of the reception signal, PA1 To judge reliability of the received signal etc.
Next, operations of the conventional pattern matching apparatus shown in FIG. 9 will now be explained with reference to FIG. 11. In FIG. 11, symbol x(kT) indicates the received signal.
At a Time Instant 0T
An input signal x(0T) is multiplied by coefficients a0, a1, a2, a3, and a4. Since an initial value of D-FF 623 is equal to 0, an output y(0T) is given by y(0T)=a4*x(0T). At this time, since the quantity of input data is not equal to that of the patterns, no UW pattern detection decision is carried out.
At a Time Instant 1T
Since an initial value of a D-FF located at one preceding stage is equal to 0, the multiplication results between the input signal x(0T) and the coefficients a0, a1, a2, a3, and a4 are stored into the D-FF respectively. Another input signal x(1T) is multiplied by the coefficients a0, a1, a2, a3, and a4. Since the value of the D-FF 623 is equal to a3*x(0T), an output y(1T) is given by y(1T)=a3*x(0T)+a4*x(1T). At this time, since the quantity of the input data is not equal to that of the patterns, no UW pattern detection decision is carried out.
At a Time Instant 2T
The result of the (multiplication result) between an input signal x(1T) and the coefficient a0 is stored into a D-FF 605. An result of the (addition result) obtained by adding the 1-T preceding value of the DD-FF 605 to the multiplication result between the input signal x(1T) and the coefficient a1 is stored into a D-FF 611. Another addition result obtained by adding the 1-T preceding value of the D-FF 611 to the multiplication result between the input signal x(1T) and the coefficient a2 is stored into a D-FF 617. Another addition result obtained by adding the 1-T preceding value of the D-FF 617 to the multiplication result between the input signal x(1T) and the coefficient a3 is stored into a D-FF 623. Another input signal x(2T) is multiplied by the coefficients a0, a1, a2, a3, and a4. Since the value of the D-FF 623 is equal to: EQU a2*x(0T)+a3*x(1T),
an output y(2T) is given by: EQU y(2T)=a2*x(0T)+a3*x(1T)+a4*x(2T).
At this time, since the quantity of the input data is not equal to that of the patterns, no UW pattern detection decision is carried out.
At a Time Instant 3T
The multiplication result between the input signal x(2T) and the coefficient a0 is stored into the D-FF 605. An addition result obtained by adding the 1-T preceding value of the D-FF 605 to the multiplication result between the input signal x(2T) and the coefficient a1 is stored into the D-FF 611. Another addition result obtained by adding the 1-T preceding value of the D-FF 611 to the multiplication result between the input signal x(2T) and the coefficient a2 is stored into the D-FF 617. Another addition result obtained by adding the 1-T preceding value of the D-FF 617 to the multiplication result between the input signal x(2T) and the coefficient a3 is stored into the D-FF 623. Another input signal x(3T) is multiplied by the coefficients a0, a1, a2, a3, and a4. Since the value of the D-FF 623 is equal to: EQU a1*x(0T)+a2*x(1T)+a3*x(2T),
an output y(3T) is given by: EQU y(3T)=a1*x(0T)+a2*x(1T)+a3*x(2T)+a4*x(3T).
At this time, since the quantity of the input data is not equal to that of the patterns, no UW pattern detection decision is carried out.
At a Time Instant 4T
The multiplication result between an input signal x(3T) and the coefficient a0 is stored into the D-FF 605. An addition result obtained by adding the 1-T preceding value of the D-FF 605 to the multiplication result between the input signal x(3T) and the coefficient a1 is stored into the D-FF 611. Another addition result obtained by adding the 1-T preceding value of the D-FF 611 to the multiplication result between the input signal x(3T) and the coefficient a2 is stored into the D-FF 617. Another addition result obtained by adding the 1-T preceding value of the D-FF 617 to the multiplication result between the input signal x(3T) and the coefficient a3 is stored into the D-FF 623. Another input signal x(4T) is multiplied by the coefficients a0, a1, a2, a3, and a4. Since the value of the D-FF 623 is equal to: EQU a0*x(0T)+a1*x(1T)+a2*x(2T)+a3*x(3T),
and output y(4T) is given by: EQU y(4T)=a0.times.x(0T)+a1.times.x(1T)+a2.times.x(2T).times.(2T)+a3*x(3T)+a4*x (4T).
At this time, since the quantity of the input data is equal to that of the pattern, the UW pattern detection decision is commenced.
The UW pattern may be detected/judged by repeatedly performing the above-explained calculation process based upon a value y(kT) by comparing this value y(kT) with the threshold value. This value y(kT) is calculated by the following formula (1): EQU y(kT)=a0*x((k-4)T)+a1*x((k-3)T)+a2*x((k-2)T)+a3*x((k-1)T)+a4*x(kT) (1)
It should be noted that when the input signal x(kT) corresponds to digital data after the decoding operation, as represented in FIG. 12, the detection/judgement of the UW pattern may be realized not by way of the multiplications by the coefficients a0, a1, a2, a3, and a4, buy by way of an exclusive OR gating operation.